Index: math/Makefile
===================================================================
--- math/Makefile
+++ math/Makefile
@@ -605,6 +605,7 @@
     SUBDIR += rpy
     SUBDIR += rpy2
     SUBDIR += ruby-algebra
+    SUBDIR += rubygem-expression_parser
     SUBDIR += rubygem-fftw3
     SUBDIR += rubygem-narray
     SUBDIR += rubygem-narray_miss
Index: math/rubygem-expression_parser/Makefile
===================================================================
--- /dev/null
+++ math/rubygem-expression_parser/Makefile
@@ -0,0 +1,15 @@
+# $FreeBSD$
+
+PORTNAME=	expression_parser
+PORTVERSION=	0.9.0
+CATEGORIES=	math rubygems
+MASTER_SITES=	RG
+
+MAINTAINER=	ruby@FreeBSD.org
+COMMENT=	Mathematical expression parser for Ruby
+
+USE_RUBY=	yes
+USE_RUBYGEMS=	yes
+RUBYGEM_AUTOPLIST=	yes
+
+.include <bsd.port.mk>
Index: math/rubygem-expression_parser/distinfo
===================================================================
--- /dev/null
+++ math/rubygem-expression_parser/distinfo
@@ -0,0 +1,2 @@
+SHA256 (rubygem/expression_parser-0.9.0.gem) = 2b56db3cffc48c3337f4f29f5bc2374c86e7ba29acb40269c74bb55af9f868a4
+SIZE (rubygem/expression_parser-0.9.0.gem) = 6144
Index: math/rubygem-expression_parser/pkg-descr
===================================================================
--- /dev/null
+++ math/rubygem-expression_parser/pkg-descr
@@ -0,0 +1,4 @@
+Implementation of mathematical expression parsing in Ruby including
+support for reverse polish notation (RPN).
+
+WWW: http://lukaszwrobel.pl/blog/math-parser-part-1-introduction